The invention is in the field of mine tunneling machines, such as machines for cutting large variable cross-section mining tunnels having wide flat floors.
The most common known method of forming large mining tunnels in rock is the drill-and-blast method using explosives which has many disadvantages, one of which is that it is very hazardous. Thus, there has been a long-felt need for a mobile mining machine capable of successfully cutting large mining tunnels in rock by mechanical means in order to replace the use of explosives.
Several prior art patents show mining machines which appear to be capable of rotating a cutterhead about a horizontal axis and/or swinging it across a work face about a vertical axis. Typical of these are Osterhus et al., U.S. Pat. No. 2,776,824; Bergmann, U.S. Pat. No. 3,307,879; Frenyo et al., U.S. Pat. No. 3,929,378; Sigott et al., U.S. Pat. No. 4,111,488, and Marten, U.S. Pat. No. 4,230,372. All of these prior art patents disclose machines employing toothed or ripper cutter elements rather than disc cutters.
Bechem, U.S. Pat. No. 4,045,088 discloses a mining machine which is characterized by oscillation of a so-called drilling head about a vertical pivot axis to arcuately drive a slot cavity, the head and the rotatable disc cutters carried thereby being oscillated through a horizontal angle of about 120.degree.. Plural disc cutters are canted in a diverging manner. No cutter movement is contemplated other than horizontal oscillation.
Stoltefuss et al., U.S. Pat. No. 3,873,157 discloses a tunneling or mining machine with the cutting device rotatably mounted on the forward end of a boom which is vertically and horizontally pivotable. The cutting arrangement involves two narrow wheels or rollers carrying pick-like cutters.
Also known is Wharton, U.S. Pat. No. 3,726,562 which discloses a coal mining machine having a cutterhead in the shape of a shallow cone rotatably mounted on the forward end of an elongate boom. The cutterhead, although not described in detail, appears to involve a series of picks as the cutting elements. It is not clear from the disclosure of the patent how the cutterhead is rotated and the patent disclosure does not contemplate any particular correlation between the rate of cutterhead rotation and the rate of cutterhead swing. The cutterhead is swingable both horizontally and vertically.
Spurgeon, U.S. Pat. 4,312,541 discloses a trench cutting machine comprising a main body assembly and a cutting wheel assembly. This coal mining machine moves plural rows of disc cutters horizontally about a substantially vertical facilitate discharge to a conveyor. A cylinder is mounted transversely on the main body assembly and carries a pair of pistons which extend axially from each end of the cylinder. Gripper pads are provided on each piston to bear against the side walls of the trench. Each piston has an end face within the cylinder which, together with an inner side wall of the cylinder, comprises a pressure chamber adapted to force the pads against the trench. The main body and its cylinder are free to move laterally relative to the pistons when the cylinder is pressurized. Extensible arms are provided between the pistons and the main body assembly for forcing the main body assembly and its cutting wheel forwardly to progessively cut a trench. A steering assembly is provided to shift the main body assembly laterally relative to the pistons and about the central axis of the cutting wheel.
Sugden et al., U.S. Pat. No. 4,548,442 teaches a mobile mining machine having a wheel-like cutterhead assembly and having a swing boom assembly located forward of a pitch boom assembly.
Co-pending U.S. patent application Ser. No. 07/706,052, including applicant Sugden of the subject application as a co-inventor, discloses a mobile mining machine having both a pitch boom assembly and a swing boom assembly in which the pitch boom assembly is attached to the cutterhead assembly, and the swing boom assembly is connected to the pitch boom assembly and to the mobile mining machine main frame. The above configuration allows the cutting of a tunnel having a low height to width ratio and optionally having no roof crown.
Co-pending U.S. patent application Ser. No. 07/701,503, including the applicants of the present application as inventors, discloses a mining machine in which a cutting wheel supporting a plurality of roller-cutters rotates about a horizontal axis and is supported on a slewing boom. The resulting tunnel has a flat floor and roof and elliptical walls. The slewing boom is supported on a main beam assembly, the front end of which rests on powered crawler tracks and the rear end of which passes through a gripper assembly which may be clamped between the floor and roof of the tunnel, and against which the main beam assembly may be urged forward for engaging the roller-cutters with the mining face. A preload crawler is urged against the roof of the tunnel above the powered crawler tracks to locate the main beam assembly rigidly relative to the tunnel such that the roller-cutters may cut the rock in the mining face with minimal loss of cutting force due to vibration.
Seberg, U.S. Pat. No. 3,976,703 discloses a cutting wheel supported on a pair of spaced supporting trucks, while App, U.S. Pat. No. 1,290,479 utilizes a chain-driven cutting wheel supported on a rail-mounted carriage. Auger-type cutters supported on a crawler-undercarriage form the basis of the mining machine disclosed by Bredthauer, U.S. Pat. No. 3,290,095. Fink, U.S. Pat. No. 4,035,024 utilizes roller-type cutters mounted on the periphery of a horizontal cutting wheel to cut a shallow trench in hard rock. While such roller-cutters are more effective and longer-lasting than picks in cutting hard rock, the cutting wheels could not slew, and the carriage supporting the wheels advanced against a support frame clamped to the walls of the trench.
A need thus exists for a mobile mining machine having a pitch boom assembly and a swing boom assembly in which the swing axis is tilted relatively forward, away from vertical. The tilted swing axis of the present invention thus cuts tunnels having large, variable cross-sections and wide, flat floors.
A need also exists for a mobile mining machine having the above described tilted swing boom that is convertible into a swing boom having a substantially vertical swing axis.